On Github, @rlandgrebe reported an issue when trying to rewrite URLs
that contained query strings.
With the PHP language module we were in fact segfaulting (SIGSEGV) in
libphp
[93960.462952] unitd[20940]: segfault at 7f307cef6476 ip 00007f2f81a94577 sp 00007fff28a777d0 error 4 in libphp-8.2.so[7f2f818df000+2fd000] likely on CPU 0 (core 0, socket 0)
#0 0x00007f2abd494577 in php_default_treat_data (arg=1, str=0x0,
destArray=<optimized out>)
at /usr/src/debug/php-8.2.10-1.fc38.x86_64/main/php_variables.c:488
488 if (c_var && *c_var) {
(gdb) p c_var
$1 = 0x7f2bb8880676 <error: Cannot access memory at address 0x7f2bb8880676>
This was when trying to get the query string which somehow is pointing
off into the woods.
This gdb debug session when doing rewrite basically shows the core of
the issue
(gdb) x /64bs req->fields
...
0x7f7eaaaa8090: "GET"
0x7f7eaaaa8094: "HTTP/1.1"
0x7f7eaaaa809d: "::1"
0x7f7eaaaa80a1: "::1"
0x7f7eaaaa80a5: "8080"
0x7f7eaaaa80aa: "localhost"
0x7f7eaaaa80b4: "/test?q=a"
0x7f7eaaaa80be: "/test"
...
(gdb) p target_pos
$4 = (void *) 0x7f7eaaaa80b4
(gdb) p query_pos
$6 = (void *) 0x7f7eaaaa6af6
(gdb) p r->args->start
$8 = (u_char *) 0x7f7ea4002b02 "q=a HTTP/1.1\r\nHost: localhost:8080\r\nUser-Agent: curl/8.0.1\r\nAccept: */*\r\n\r\n"
(gdb) p r->target.start
$9 = (u_char *) 0x7f7ea40040c0 "/test?q=a"
That last address, 0x7f7ea40040c0, looks out of wack, it should be
smaller than r->args->start.
That results in a calculation in nxt_router_prepare_msg()
if (r->args->start != NULL) {
query_pos = nxt_pointer_to(target_pos,
r->args->start - r->target.start);
nxt_unit_sptr_set(&req->query, query_pos);
} else {
that goes negative that then is stored in req->query.offset which is a
uint32_t and so wraps backwards from UINT_MAX to give us an offset of a
little under 4GiB, hence the above invalid memory access.
All this happens due to in nxt_http_rewrite() if we have a URL with a
query string, we create a new memory allocation to store the transformed
URL and query string.
We set r->target to point to this new allocation, but we also need to
point r->args->start to the start of the query string in this new
allocation.
Reported-by: René Landgrebe <https://github.com/rlandgrebe>
Tested-by: René Landgrebe <https://github.com/rlandgrebe>
Tested-by: Liam Crilly <liam.crilly@nginx.com>
Fixes: 14d6d97b ("HTTP: added basic URI rewrite.")
Closes: <https://github.com/nginx/unit/issues/964>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>
NGINX Unit
Universal Web App Server
NGINX Unit is a lightweight and versatile open-source server that has two primary capabilities:
- serves static media assets,
- runs application code in seven languages.
Unit compresses several layers of the modern application stack into a potent, coherent solution with a focus on performance, low latency, and scalability. It is intended as a universal building block for any web architecture regardless of its complexity, from enterprise-scale deployments to your pet's homepage.
Its native RESTful JSON API enables dynamic updates with zero interruptions and flexible configuration, while its out-of-the-box productivity reliably scales to production-grade workloads. We achieve that with a complex, asynchronous, multithreading architecture comprising multiple processes to ensure security and robustness while getting the most out of today's computing platforms.
Quick Installation
macOS
$ brew install nginx/unit/unit
For details and available language packages, see the docs.
Docker
$ docker pull unit
For a description of image tags, see the docs.
Amazon Linux, Fedora, RedHat
$ wget https://raw.githubusercontent.com/nginx/unit/master/tools/setup-unit && chmod +x setup-unit
# ./setup-unit repo-config && yum install unit
# ./setup-unit welcome
For details and available language packages, see the docs.
Debian, Ubuntu
$ wget https://raw.githubusercontent.com/nginx/unit/master/tools/setup-unit && chmod +x setup-unit
# ./setup-unit repo-config && apt install unit
# ./setup-unit welcome
For details and available language packages, see the docs.
Running a Hello World App
Unit runs apps in a variety of languages. Let's consider a basic example, choosing PHP for no particular reason.
Suppose you saved a PHP script as /www/helloworld/index.php:
<?php echo "Hello, PHP on Unit!"; ?>
To run it on Unit with the unit-php module installed, first set up an
application object. Let's store our first config snippet in a file called
config.json:
{
"helloworld": {
"type": "php",
"root": "/www/helloworld/"
}
}
Saving it as a file isn't necessary, but can come in handy with larger objects.
Now, PUT it into the /config/applications section of Unit's control API,
usually available by default via a Unix domain socket:
# curl -X PUT --data-binary @config.json --unix-socket \
/path/to/control.unit.sock http://localhost/config/applications
{
"success": "Reconfiguration done."
}
Next, reference the app from a listener object in the /config/listeners
section of the API. This time, we pass the config snippet straight from the
command line:
# curl -X PUT -d '{"127.0.0.1:8000": {"pass": "applications/helloworld"}}' \
--unix-socket /path/to/control.unit.sock http://localhost/config/listeners
{
"success": "Reconfiguration done."
}
Now Unit accepts requests at the specified IP and port, passing them to the application process. Your app works!
$ curl 127.0.0.1:8080
Hello, PHP on Unit!
Finally, query the entire /config section of the control API:
# curl --unix-socket /path/to/control.unit.sock http://localhost/config/
Unit's output should contain both snippets, neatly organized:
{
"listeners": {
"127.0.0.1:8080": {
"pass": "applications/helloworld"
}
},
"applications": {
"helloworld": {
"type": "php",
"root": "/www/helloworld/"
}
}
}
For full details of configuration management, see the docs.
OpenAPI Specification
Our OpenAPI specification aims to simplify configuring and integrating NGINX Unit deployments and provide an authoritative source of knowledge about the control API.
Although the specification is still in the early beta stage, it is a promising step forward for the NGINX Unit community. While working on it, we kindly ask you to experiment and provide feedback to help improve its functionality and usability.
Community
-
The go-to place to start asking questions and share your thoughts is our Slack channel.
-
Our GitHub issues page offers space for a more technical discussion at your own pace.
-
The project map on GitHub sheds some light on our current work and plans for the future.
-
Our official website may provide answers not easily found otherwise.
-
Get involved with the project by contributing! See the contributing guide for details.
-
To reach the team directly, subscribe to the mailing list.
-
For security issues, email us, mentioning NGINX Unit in the subject and following the CVSS v3.1 spec.